In some cases, you want better control over when exactly your form is submitted
and what data is passed to it. Instead of using the
handleRequest()
method, pass the submitted data directly to
submit():

Forms consisting of nested fields expect an array in
submit(). You can also submit
individual fields by calling submit()
directly on the field:

$form->get('firstName')->submit('Fabien');

Tip

When submitting a form via a "PATCH" request, you may want to update only a few
submitted fields. To achieve this, you may pass an optional second boolean
argument to submit(). Passing false will remove any missing fields
within the form object. Otherwise, the missing fields will be set to null.

Caution

When the second parameter $clearMissing is false, like with the
"PATCH" method, the validation extension will only handle the submitted
fields. If the underlying data needs to be validated, this should be done
manually, i.e. using the validator.